Preparation of epoxy-anhydride compositions from an epoxy resin and an acid anhydride containing two cyclic and one linear anhydride group

ABSTRACT

PREPARATION OF EPOXY-ANHYDRIDE COMPOSITION BY REACTING AN EPOXY RESIN WITH AN ACID ANHYDRIDE CONTAINING TWO CYCLIC AND ONE LINEAR ANHYDRIDE GROUP. THE ACID ANHYDRIDE HAS THE FORMULA:   1,3-DI(O=),6,9A-DI(CH3-),6-((1,3-DI(O=),6,9A-DI(CH3-),12-   (CH3-CH(-CH3)-)-3,3A,4,5,5A,6,7,8,9,9A,9B,10,11,11A-   TETRADECAHYDRO-1H-3B,11-ETHENOPHENANTHRO(1,2-C)FUR-6-   YL)-CO-O-CO-),12-(CH3-CH(-CH3)-)-3,3A,4,5,5A,6,7,8,9,9A,   9B,10,11,11A-TETRADECAHYDRO-1H-3B,11-ETHENOPHENANTHRO-   (1,2-C)FURAN   THE REACTION PRODUCT IS THERMO HARDENED AT 80-210*C.

United States Patent "ice Patented ,fgffiil? 3,582,509 Hence, said anhydrides have been used as hardening PREPARATION OF EPOXY ANHYDRIDE C0MP0 agents in epoxy compositions, where good mechanicaland SITIONS FROM AN EPOXY RESIN AND AN dielectnc properties at elevated temperatures are required. ACID ANHYDRIDE CONTAINING TWO CYCLIC The following acid anhydrides have been used to harden AND ONE LINEA ANHYDREDE G O 5 epoxy resins: phthalic, maleic, chloromaleic, dichloro- Henryk Staniak, Blonie k, and Piotr Penczek, Warsaw, maleic, tctrachlorophthalic, tetrahydrophthalic, dimeth- Poland, assignors to Instytut Tworzyw Sztucznych, Waryltetrahydrophthalic, butenyltetrahydrophthalic, chlorotet- P0131?! rahydrophthalic, endomethylenetetrahydrophthalic, hexa- 15111;) Drawl ng. Filed (get-r14, 9?8, 1 6 2 -18 155} chloro-endo-methylenetetrahydrophthalic, methyl endopmmty f g g c 0 methylene-tetrahydrophthalic, hexahydrophthalic and dohm CL C07c cosc 9/18 1 decenylsuccinic anhydride and pyromellitic dianhydride. s CL 9 Claims Compositions hardened with acid anhydrides mentioned above, however, show several defects, considering their technological and processing properties in the hardening operation as well as usable qualities of hardened com- ABSTRACT OF THE DISCLOSURE positions including for example: a high melting point, Preparation of epoxy-anhydride composition by reactpoor solubility in epoxide resins, too high or too low ing an epoxy resin with an acid anhydride containing two reactivity, sublimation of an anhydride during heating, cyclic and one linear anhydride group. The acid anhytoxicity of an anhydride and a great brittleness or a reladride has the formula: tively low heat resistance of a hardened composition.

0 on i J d 3 a f l CH-C O i 1 H 0 0 H O CH(CHa)2 C a)2 HC CHC O O The reaction product is thermo hardened at 80-2l0 C. Generally epoxide compositions hardened with compounds mentioned above have the imperfection of shrinkage in hardening, which, while lower indeed than in other The invention relates to the preparation of thermocasting resins such as e.g. unsaturated polyester resins, hardening compositions, having epoxide resins and an acid nevertheless does cause internal stresses, cracking of coatanhydride as main components. The said thermohardenings and often undesirable changes of dimensions too. ing compositions distinguish themselves by an advan- In accordance with this inveniton, epoxy-anhydride tageous complex of technological and processing prop- 40 compositions devoid of a majority of defects mentioned erties. above can be obtained by use of an acid anhydride having They are mostly used 'for casting, encapsulating and the chemical formula ii/ \i CH 0 CH3 0 I l oHo O \/.I\ l H3O C H3O l \O CH(CHa)2 CH(CH;4)2 CHO HC impregnating and also as adhesives and binding materials as a hardening agent. for laminates. This anhydride contains components of resin acids of Epoxide resins have been previously hardened by means rosin, particularly the diene adduct of levopimaric acid of primary and secondary amines and aliphatic and aroand maleic anhydride is in the molecule.

matic polyamines or tertiary amines, polycarboxylic acids, The molecule contains two cyclic and one linear anhy- 6O cycllc anhydrides or dicarboxylic acids, polyanhydrldes dride groups.

of dicarboxylic aliphatic acids, diphenols and phenol- The acid anhydride having this formula accordingly formaldehyde resins, polyaminoamides, polymercaptans is not hitherto known (although the products obtained and complexes of Lewis acids. by the diene reaction of resin acids derived from rosin and maleic anhydride as well as the crystalline diene The most frequently used curing agents have been aliadduct of levopimaric acid and maleic anhydride isolated phatic amines and acid anhydrides.

Aliphatic amines effect hardening at room temperature; therefrom, which contains one cyclic anhydride group but compositions thus hardened show a relatively low and one carboxyl group in the molecule are known). heat resistance. On the other hand, compositions hardened This acid anhydride can be obtained in a process acwith acid anhydrides are hardened at elevated temperacording to the invention in two different ways, wherein tures and have heat resistance which is far higher than in the variants a rosin, resin acid, derived from rosin or compositions hardened by means of aliphatic polyamines. purified abietic acid are used as starting materials.

According to the first varient, one of the said starting materials is heated with acetic anhydride. Acetic acid formed in the reaction and an excess of acetic anhydride are distilled off while the remainder is a mixture of resin acid anhydrides or abietic anhydride, depending on the starting material used. The remainder is subsequently heated :with maleic anhydride. Maleic anhydride is used in quantity close to the stoichiometric one, namely 15.0l6.8, of maleic anhydride per 100 g. of the said anhydrides mentioned above obtained from resin acid derived from rosin.

Heating with maleic anhydride is carried out at a temperature of 100-260 C. preferably with gradually raising of the temperature in successive stages of the process. In the course of heating isomerization to levopimaric anhydride and afterwards diene addition of two molecules of maleic anhydride to a molecule of levoprimaric anhydride occur.

The thus obtained products are not pure and the mixtures have a consistency close to that of rosin.

The second variant of preparing acid anhydride having a structure set forth above consists in heating of the known diene adduct of resin acids derived from rosin and maleic anhydride with acetic anhydride. The acetic acid formed and an excess in the reaction of an acetic anhydride are distilled off.

As starting materials, diene adducts obtained from various kinds of resin or from purified abietic acid can be used. The said adducts having a consistency close to rosin are used as a crude mixture in form of the crystalline diene adduct of levopimaric acid and maleic anhydride, being isolated by crystallization from products of heating of rosin, its resin acids or purified abietie acid with maleic anhydride.

In order to facilitate mixing of the acid anhydride, obtained according to the invention, with epoxide resins advantageously the said acid anhydride is first melted with one of the acid anhydrides previously used for hardening epoxide resins; particularly the liquid acid anhydride or acid anhydride having a low melting point.

A considerable lowering of the softening point of a hardener and a reduction of viscosity after melting is thereby obtained. In compositions according to the invention the following known acid anhydrides are used as additional hardeners: hexahydrophthalic, tetrahydrophthalic, endomethylenetetrahydrophthalic, methylendomethylenetetrahydrophthalic, dimethyltetrahydrophthalic, dodecenylsuccinic and maleic anhydride.

These anhydrides are used in a quantity from to 200, advantageously from -50 parts by weight per 100 parts by weight of acid anhydride having the formula set forth above. The total quantity of acid anhydride per one epoxide group of a resin is established by the stoichiometric calculation in a similar way as for known epoxide resin compositions, hardened with acid anhydrides.

Compositions obtained from epoxide resin, acid anhydride having a formula as set forth above and possibly other acid anhydrides are relatively rigid and frail as are known non-fiexibilized epoxide resin compositions, hardened with acid anhydrides. In order to flexibilize the compositions according to the invention, known flexibilizers, such as azelaic, sebacic or brassylic polyanhydrides, mixtures of said anhydrides and oligoanhydrides obtained by heating products of dimerization, polymerization or copolymerization of unsaturated acids with acetic anhydride, polysulphides and acid anhydride end groups, linear or branched polyesters having carboxyl or acid anhydride end groups or and also polyglycols are introduced therein.

In order to lower the viscosity of compositions of the invention it is advantageous to add diluents commonly used in known epoxide compositions such as phenylglycidyl ether and vinylcyclohexene dioxide.

The known accelerators for epoxide resins hardened with acid anhydrides may be also added to compositions of the invention. For this purpose the most suitable are tertitary amines such as dimethylaniline, benzyldimethylamine and tris (dimethylaminomethyl) phenol and also organic sulphur compounds, e.g. mercaptobenzothiazol or organic stannic compounds. The last compounds are used in the first place in compositions with cycloaliphatic epoxide resins. The known fillers may be introduced to compositions according to the invention. They are e.g. silica fiour, porcelain powder and aluminum oxide or fibrous fillers which are glass fibre in various forms.

The acid anhydride having a structure as set forth above may be used for hardening of all known kinds of epoxide resins i.e. resins and chemical compounds containing on an average more than one epoxide group in the molecule which is directly bonded with cyclohexane, bicyclo (2.2.1) heptane or cyclopentane ring, in the form of glycidyl ether, or epoxyethyl group bonded with a hydrocarbon chain or hydrocarbon ring or in form of epoxyethylene group in a hydrocarbon chain.

Epoxide resins used in compositions according to the invention are mainly lowor average-molecular-weight resins made of bisphenol A and epichlorohydrin, epoxynovolaks (reaction products of novolaks and epichlorohydrin) (3,4 epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6 methyl cyclohexane carboxylate, 3,4-epoxy-6-methylcyclohexyl epichlorohydrin, 3,4-epoxy-6-methylcyclohexyl) methyldicyclopentadiene dioxide and epoxidized butadiene oligonmers. The said compositions according to the invention are hardened at temperatures which are usual for epoxide-anhydride compositions i.e. -210" C. advantageously in the range of -180".

Additional hardening at the temperature of about 180 C. advantageously effects the heat resistance of said compositions and improves their dielectric properties at elevated temperatures. The thermohardened epoxide-anhydride compositions according to the invention can be used for various purposes, as they are close to known compositions made of epoxide resins and other acid anhydrides.

They are especially suitable for encapsulating electric devices, wherein a low hardening shrinkage of epoxide-anhydride compositions and their good electrical insulation properties at elevated temperatures are of special value.

Compositions according to the invention, especially with addition of liquid and low-melting acid anhydrides are also suitable for impregnation in electrical engineering as the advantages of said compositions mentioned above are of outstanding importance. The said compositions may be also used as adhesives for metals and may be disposed in form of solutions or powders.

Compositions according to the invention in form of solutions and containing hardening accelerators, after precondensation, are suitable as binders for glass fibre reinforced plastics and manufactured by compression moulding at an elevated temperature and also for thermohardening moulding compounds.

EXAMPLE I 120 g. of balmy resin having a melting point of 58 C. and 300 g. of acetic anhydride are heated up to the boiling point for 5 hours. Subsequently a mixture of an acetic acid and acetic anhydride is distilled oft under a decreased pressure. The obtained product, having the melting point 43 C. is heated with 36 g. of maleic anhydride, while raising gradually for 1 hour up to 220 C. Subsequently a slight amount of volatile matters is distilled off. An acid anhydride in form of a frail brown resin having the melting point of 87 C. is obtained in an almost theoretical yield.

EXAMPLE II 1230 g. of balmy resin and 379 g. of maleic anhydrides are heated at the temperature of C. After raising the temperature up to 220 C. the mixture is heated at this temperature for 1 /2 hours and then a slight amount of volatile matters is distilled off under a decreased pressure. 800 g. obtained diene adduct and 800 ml. of acetic anhydride are heated within 4 hours up to the boiling point. Subsequently acetic acid and acetic anhydride are distilled 6 off at first under normal and then under decreased pres- Volume resistivity: sure. The acid anhydride in form of a frail, brown resin 1 3 1015 ohm cm C is obtained within an almost theoretical yield. b ohm cm C EXAMPLE III 1.1.10 ohm cm./130 C.

4.10 ohm cm./155 C.

i o 5 100 g. low molecular weight blsphenol A epichlorohy 1.41011 ohm Cub/180 C.

drin epoxide resin Epidiah 5 product of Zaklady Chemiczene Sarzyna, Poland having epoxide groups content of We claim: 0.50 gram equivalent/100 g. of resin and 131 g. acid an- 1. A method of preparing epoxide-anhydride composihydride obtained as given in Example I or II are melted tions which comprises mixing an epoxide resin which conand subseq'ilently 0.3 g. of benzyl dimethylamine are tains more than one epoxy group on the molecule with an added. T he'gel time of the obtained composition is 45 minacid anhydride of the formula CH5 CH3 -CHC I CHC// mo H30 1 -cH(cHi)2 CH(CH3)2 HC H-C utes at 130 C. The composition is cured at 130 C. for and hardening the resulting mixture at a temperature in hours and post-cured at 150 C. for 4 hours. the range of 80-210 C.

Characteristics of the obtained product: A methpd P i F tions as claimed n clalm 1 wherein a st01ch1ometr1c Linear shrinkage on curing: 0.15% amount of said acid anhydride is present per one epoxide Glass temperature: 112 C. determined by the thermogroup of said epoxide resin.

mechanical method. 3. A method of preparing epoxide-anhydride composi- Dielectric less factor at frequency 70 N2: tions as claimed inclaim 1 wherein said resin is hardened s'f at a temperature in the range of 120-180" C. OOIS-Ghm elm/105.. 4. A method according to claim 1 wherein said acid 005 h (mm/120 anhydride 18 prepared by heating a material selected from (L066 hm elm/130s thegroup consistiij g of rosin, resin aclds derived from 055 ohm IL/155.. C. 40 T0811], and abietic ac d, in the presence of acetic anhydride, distilling ofi the acetic acid formed in the reaction and Volume re1St1V1tY1 an excess of acetic. anhydride and subsequently heating 4 1016 b 20 C. the obtained product with maleic anhydride in amount of 740 4 1 /105 C 15.0-16.8 g. maleic anhydride per 100 g. of the said 8 1()13 ohm 120 product, at a temperature in the range of -260 C. 3,10 oh /130 C. 5. An acid anhydride containing two cyclic and one 5.10 ohm cm./155 C. linear anhydride group of the structure o o\ 0 CH3 h -CHC I Gil-0 H30 \0 H3O \O m Hah CH(CH H-C EXAMPLE IV 6. A method of preparing the acid anhydride as set forth in claim 5, which comprises heating an acid anhy- 5 dride, obtained from a material selected from the group consisting of rosin, resin acids derived from rosin and abietic acid, with maleic anhydride at a temperature in A composition as in Example III is cured at 130 C. for 20 hours and post-cured at 180 C. for 24 hours.

Characteristics of the obtained product:

Linear shinkage on curing: 0.6% the range f 100-2 0 Glass temperature: 7. A method of preparing the acid anhydride as set Dlelectrlclessfactoratfrequency 70 NE '70 forth in claim 6 wherein 15.0-16.8 g. of maleic acid is 0,0046 h C, employed per 100 g. of the product acid anhydride. 0.0070 ohm cm./ C. 8. The method of preparing the acid anhydride set forth 0.018 ohm cm./ C. in claim 5, which comprises reacting a diene adduct of 0.062 ohrn cm./ C. resin acids derived from rosin and maleic anhydride with 0.073 ohm cm./ C. 75 acetic anhydride at 100-260 C., distilling off acetic acid 7 8 formed in the reaction and removing an excess of acetic FOREIGN PATENTS anhydride y distillation 785,311 5/1968 Canada 260-4466 9. The method of claim 8 wherein said diene adduct is 1,070,866 6/ L967 Great Britain 260--346.6 a crystalline diene adduct of levopimaric acid and maleic OTHER REFERENCES anhydride, isolated by crystallization of products obtained 5 u by heating the material selected from the group consist- Harms ct Rosin & Rosln Derlvatlves," feprlnt 0f ing of rosin, resin acids derived from rosin and purified Pages 789492 of Encyclopedia of Chemical Technology abietic acid with maleic anhydride. (1953) 10 DONALD E. CZAI A, Primary Examiner References Cited R. W. GRIFFIN, Assistant Examiner UNITED STATES PATENTS 2,039,243 4/1936 Krzikalla etal. 260-101 2,818,412 12/1957 Eckhardt et al. 260-346.6 15 117-126, 168;26047, 101, 346.6 

